The secretion of protein material in the parasympathetic submaxillary saliva

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This paper deals with a study of the secretion of protein material by the submaxillary gland of the cat in response to electrical stimulation of the chorda tympani nerve. In the attempt to make a more generous use of certain advantages offered by physical methods in research on the digestive glands, the submaxillary gland was chosen for the initial investigation because of the relative ease of physiological experimentation. The study is characterized by (1) the use of quantitative spectroscopic methods of analysis which permit an extension in the range of the investigation over that possible with a purely chemical procedure, and (2) the application of mathematical analysis in the interpretation of the results. The work of previous investigators (Heidenhain 1868, 1878, 1883; Werther 1886; Langley and Fletcher 1890; Gregerson and Ingalls 1931) has shown that with increasing intensity of the stimulus the para­-sympathetic submaxillary saliva becomes more concentrated in (1) inorganic salts which are presumably derived from the tissue fluids and ultimately from the blood, and (2) organic material, provided that the stores in the gland are not too much depleted by previous stimulation. The con­centration changes in the former group of substances are presumably connected with phenomena occurring at the glandular membranes; those in the latter group obviously cannot be accounted for by a simple washing out of stored material from the gland, but must result from the operation of a more complicated secretion mechanism. In the attempt to gain a better understanding of the fundamental nature of the secretion processes, we have determined spectroscopically the relative concentrations of protein material, and the Na and K concentrations in samples of saliva obtained in response to various intensities of stimulation of the chorda tympani nerve. Many of the samples were also analysed chemically for protein and non-protein nitrogen, chlorides, and acid-combining power. These sub­stances, along with water, are the main constituents of the submaxillary saliva as obtained in our experiments. A long series of relatively small samples of secretion was taken from each animal; this feature of the experimental technique is considered to be important, viz. under such conditions one may best determine the changes in composition resulting from the variation of one factor only—the intensity of the stimulus—since changes in other factors which are not directly controlled are small from sample to sample.